1. Field of the Invention
The present invention relates to an apparatus and method for controlling the temperature of a surface in a processing chamber. More specifically, the invention relates to methods and apparatus for controlling the temperature of an energy transparent window or electrode of a processing chamber.
2. Background of the Related Art
Many processes for fabricating integrated circuits and other electronic devices, such as etching, chemical vapor deposition, and physical vapor deposition, are plasma-enhanced or plasma-assisted. These processes employ process gases which are excited to a plasma state within a vacuum chamber. As one example, plasma etching (typically referred to as “dry” etching) has become a well accepted process in semiconductor manufacturing. The etching process removes patterned material from the substrate surface located in a substrate processing system. Gases are the primary dry etch medium, and plasma energy is used to drive the reaction. The plasma is created by applying an electrical field to a gas or combination of gases. Inside the chamber, the substrate to be processed is placed on a negatively charged cathode. Positively charged ions from the plasma are attracted and accelerated toward the cathode's negative charge, and the ions impact the substrate surface. The ability to attract ions in a direction normal to the substrate surface allows manufacturers of integrated circuits and other electronic devices to achieve high quality, vertical etching profiles.
The plasma etch process occurs in two ways, either separately or in combination, depending on the material to be etched and the etch chemistry used: (1) chemically reactive ions and free radicals formed in the plasma strike the substrate surface where they react with the surface material and form volatile compounds which can be exhausted from the system; and (2) the ions may be attracted to the substrate surface and strike the substrate surface with sufficient impact energy to break the chemical bonds in the film, physically dislodging or “sputtering” material from the substrate surface.
In a plasma processing chamber, radio frequency (RF) electromagnetic energy is used to generate and maintain a plasma within the processing chamber. It is often necessary to control temperatures of surfaces within the process chamber. This is particularly true in the case of a reactor chamber having a chamber lid which acts as either an electrode or a window (window/electrode) for admitting RF power from an inductive antenna therethrough. For example, the chamber lid temperature tends to rise during plasma generation, due to heat absorption from the plasma and RF energy being coupled into the plasma. The plasma may cause the chamber components, such as the electrode or window, to approach temperatures of 660° C. and higher. The etch rate and etch selectivity can change as the temperature in the chamber changes. For example, the etch rate of oxides can decrease due to an increase in chamber temperature until eventually the etching may stop.
In addition, in some cases where the window/electrode is a semiconducting material, it may be necessary to control the temperature of the window/electrode within a particular temperature range to obtain the proper electrical properties of the window/electrode. The application of RF power to generate and maintain the plasma leads to heating of the surfaces within the chamber, including windows or electrodes or for combination window/electrodes.
Prior efforts to effectuate temperature control of chamber components, such as windows and electrodes made of dielectric, non-metallic or semiconductive materials, have centered around indirect cooling which relies on thermal conduction of heat from the chamber components to a heat sink such as a cooled metallic body or cooling channels formed in the antennae or coils themselves. Attempts to provide temperature, control in a processing chamber are shown in U.S. Pat. Nos. 5,863,376 and 5,074,456. However, these attempts to achieve temperature control have failed to directly control the temperature of a dielectric, non-metallic or semiconductive window or electrode. As a result, only indirect cooling has been achieved. Moreover, such prior attempts have caused complications and interference when overhead coils or antennas have been called for in a plasma chamber. Obviously, cooling apparatus compete for the same space or area as the coils or antenna or the cooling apparatus must be combined with the coils or antenna, limiting the optimization of either design.
Therefore, there remains a need for a method and apparatus which directly controls the temperature of a dielectric, non-metallic or semiconductive window or electrode. A further need remains to accomplish the foregoing with coil based chamber designs.